The traditional process for paving roadways with asphalt material is generally carried out by an asphalt paving machine and a number of supply trucks which transport the asphalt material from an asphalt production plant to the paving machine. The paving machine generally is self-propelled and driven by a wheeled or tracked drive system. A hopper is located at the front end of the machine to receive asphalt material from a truck, and a floating screed is located at the rear end of the machine to form the asphalt mat. A conveyor system typically comprised of slat conveyors and screw augers delivers the asphalt material from the hopper to the road base just ahead of the screed.
A typical asphalt paving machine has a hopper with a capacity of 5-15 tons, whereas a typical dump-type delivery truck has a capacity of about 20 tons. The front of the paving machine is usually provided with rollers which are adapted to engage the rear tires of a delivery truck. This arrangement enables asphalt material to be transferred from the truck to the asphalt paving machine by positioning the delivery truck in front of the paving machine and raising the dump bed of the truck to dump the asphalt material into the hopper as the paving machine pushes the truck along in front of it. Because the delivery truck usually carries more asphalt material than the hopper can receive at one time, the paving machine may push the delivery truck along for several minutes while its conveyor system transports the asphalt material out of the hopper to the roadway in front of the screed.
Sometimes, problems may arise when operating the paving machine and the delivery trucks in this manner. Because of traffic conditions and other unforeseen delays, it is not uncommon for the paving machine to empty its hopper of asphalt material before a loaded delivery truck is available to begin dumping its asphalt material into the hopper. When this occurs, the paving machine must stop paving and await the arrival of another delivery truck. Even if one or more loaded delivery trucks are available to dump asphalt material into the paving machine hopper, it may be necessary to stop the paving machine. Sometimes, it is simply impossible for the truck drivers to remove an empty delivery truck from engagement with the front of the paving machine and to maneuver a loaded truck into position to dump into the hopper before the hopper is emptied.
It is known to provide paving machines with receiving hoppers that have wings or other structures that can be tilted about a generally horizontal axis to urge material into the conveyor underneath the middle of the hopper. Such constructions are described in U.S. Pat. No. 6,193,437 and No. 8,936,145. The tilting of these wing structures will sometimes result in spillage of material from the hopper onto the roadway and will sometimes result in some material remaining in the hopper in the vicinity of the tilt hinges.
As is known to those having ordinary skill in the art to which the invention relates, when a paving machine stops, even for a short time, the screed will tend to settle into the freshly laid asphalt mat. Then, when the paving machine resumes its forward motion, the screed will tend to ride upwardly momentarily, thus depositing an excessive amount of asphalt material on the roadway. Consequently, stopping of the paving machine causes a depression and a bump in the surface of the asphalt mat, resulting in an uneven pavement surface. Therefore, in recent years, material transfer vehicles have been employed to shuttle asphalt material between the delivery trucks and the paving machine. Such a material transfer vehicle is described in various embodiments in U.S. Pat. No. 4,818,139, No. 5,015,120, and No. 5,035,534, which are incorporated herein by reference. These patents describe a self-propelled material transfer vehicle which includes a large-capacity truck-receiving hopper and a large-capacity truck-unloading conveyor extending from this hopper to a surge bin that is sized to hold the entire load of a delivery truck. A conveyor in the surge bin is adapted to transfer asphalt material to a paver-loading conveyor that is pivotable about an essentially vertical axis so that the transfer vehicle can be positioned alongside an asphalt paving machine that is laying an asphalt mat and rapidly discharge a truckload of asphalt material into the paver's hopper. Because of its rapid loading and unloading capabilities, the material transfer vehicle can rapidly shuttle between delivery trucks at a pick-up point and a paving machine that is laying an asphalt mat so that there is less likelihood that the paving machine will have to stop paving because of a lack of asphalt material.
Because the material transfer vehicle travels on the roadway like the delivery trucks from which it obtains asphalt material, its dimensions must conform to state and federal highway standards for on-road vehicles. Consequently, the truck-receiving hopper of a material transfer vehicle may be the same width as the dump body of a delivery truck. This requires the driver of the delivery truck to maneuver his vehicle to precisely align the dump body with the truck-receiving hopper of the material transfer vehicle. This can be a time-consuming operation, and it may result in spillage of some of the asphalt material from the truck onto the roadway adjacent to the truck-receiving hopper.
The Vögele MT 3000 material transfer vehicle has a truck-receiving hopper that includes rigid sidewalls, each of which is attached to a portion of a rigid rear hopper wall. The hopper auger of this machine, which assists in moving material to the adjacent conveyor, is provided in two sections. Each hopper auger section is supported only at the sidewall, extends across a portion of the width of the hopper and is unsupported at its far end. The sidewalls are adapted to move towards and away from each other so as to vary the width of the entire truck-receiving hopper. Such a construction will allow a delivery truck driver some leeway in aligning the dump body of his truck with the truck-receiving hopper. However, the hopper auger construction is more complicated and expensive than is the hopper auger that is provided in two sections which are supported at both ends, as is found in a typical material transfer vehicle, and it requires more maintenance than a conventional hopper auger.
It would be advantageous if a system and apparatus could be provided that would allow the driver of the delivery truck more flexibility in unloading into the truck-receiving hopper of a material transfer vehicle, while also providing a hopper structure that is reliable and relatively inexpensive to build.